WO2004023603A1

WO2004023603A1 - Earth connection

Info

Publication number: WO2004023603A1
Application number: PCT/GB2003/003857
Authority: WO
Inventors: Clive Robinson
Original assignee: Hcl Fasteners Ltd.; Byron International Ltd.
Priority date: 2002-09-06
Filing date: 2003-09-08
Publication date: 2004-03-18
Also published as: GB0220765D0; GB2407926B; AU2003260785A8; GB2407926A; GB0504006D0; AU2003260785A1

Abstract

The present invention provides a clip (18) for establishing a connection between an earth bond cable (12) and extraneous metalwork (16) or other conductive object. The clip (18) comprising a flexible strap (20) having two ends, a first mating connector (22) secured at the first end of the strap (20) and a second mating connector (24) secured at the second end of the strap (20). The two connectors mate with each other to form the clip (18) into a closed loop and secure the strap (20) around the conductive object (16). The clip (18) has at least one opening extending through the clip (18), preferably through the strap (20); an electrically conductive earth bond cable (12) is fed through the opening and the clip (18) is then secured to the conductive object (16) by inter-engaging the mating connectors (22, 24) so as to clamp the earth bond cable (14) between the clip (18) and the conductive object (16).

Description

EARTH CONNECTION

The present invention relates to an arrangement for establishing an electrical system earth connection to extraneous metalwork within an electrical installation, for example to hot and cold metallic pipe work within a domestic house or industrial or office building.

The earth connection (or bond) between the electrical system earthing circuit within a building and extraneous metalwork e.g. pipe work, within that building is currently achieved by a metallic pipe clamp that is installed around the metalwork concerned. The main body of the metallic pipe clamp has a cable-terminating tag consisting of a female screw thread that engages a large headed machine screw extending through the tag. The earth bond cable is electrically connected to the tag by stripping the insulation off the end of the earth bond cable and placing it between the head of the machine screw and the tag and tightening the machine screw down to effect a connection. Unfortunately, electricians do not always terminate the earth bond cable correctly to effect a sound and longstanding electrical connection; often there is insufficient stripped cable under the head of the machine screw. The result is a connection of dubious integrity.

UK patent no. 1,600,601 describes a clip for securing a hose to a spiggot; the clip has a strap and, at one end of the strap, a tongue with a row of teeth on its top and bottom surfaces and, at the other end of the strap, a jaw having sets of teeth on the inside surfaces of the jaws. The tongue can be pushed lengthways between the jaws to close the clip and secure a circumferential fastening around a pipe or rod.

According to the present invention there is provided a clip for establishing a connection between an earth bond cable of an electrical installation and extraneous pipe work or other rounded electrically conductive object, the clip comprising a flexible strap having two ends, a first mating connector secured at the one end of the strap and a second mating connector secured at the second end of the strap, the two mating connectors being capable of mating with each other to form the clip into a closed loop and secure the strap around the conductive object, wherein the clip comprises at least one opening (which preferably extends through the strap) through which an earth bond cable can be fed, the arrangement being such that an electrically conductive earth bond cable can be fed through the opening and the clip can be secured to the conductive object by engaging the mating connectors so as to clamp the earth bond cable between the clip and the conductive object.

The term "rounded" is intended to cover conductive objects that are generally round, e.g. oval, so that the clip can press the earth bond cable against the object across the whole of the length of the cable that is passed through the opening and lies within the clip.

The conductive object will generally be a pipe or rod and will be referred to later in the specification as such but it should be borne in mind that other conductive rounded objects can be earthed in the same way.

Most preferably, the clip includes two spaced apart openings such that the earth bond cable can be threaded through one opening and out of the second opening thereby allowing the part of the cable extending through the second opening to be held in place while the clip is secured to the pipe work/rod and also ensuring that there is a guaranteed length of earth bond cable in contact with the pipe/rod corresponding to the circumferential distance between the openings along the inside perimeter of the clip.

The mating connectors of the clip are preferably rows of teeth that can interengage with each other to secure the clip around the pipe work/rod and may be as described in UK Patent No.1,606,601. The teeth can be progressively closed to provide the required clamping pressure on the earth bond cable between the pipe/rod and the clip.

The inside surfaces of the strap may include a channel for holding the earth bond cable in place while the clip is secured to the pipe/rod. If the clip includes two openings, the channel should extend between the openings. The channel may be formed by two rows of lugs, the lugs of each row being spaced apart allowing inspection of the earth bond cable once it has been clamped to the pipe/rod. Obviously, the depth of the lugs (in the direction lying along the radius of the clip when formed into a loop) should be smaller than the thickness of the earth bond cable to achieve a proper clamping pressure of the earth bond cable to the pipe/rod.

The present invention also relates to a method of securing an earth bond cable to a pipe/rod using such a clip.

A clip for securing an earth bond cable to a pipe/rod in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawings in which:

Figure 1 shows the a general arrangement of the clip for securing an earth bond cable to pipe/rod;

Figure 2 is a perspective view of the clip of Figure 1 ; Figure 3 is a face view of the clip of Figure 2; and Figure 4 is a sectional view taken through the clip.

Referring initially to Figure 1, an earth bond cable is shown by the reference number 10 and includes a conductive wire 12 covered by an insulating cover layer 14. The insulating cover layer 14 is stripped off from the end section of the cable to expose the wire 12. The wire is clamped to a series of three water pipes 16 by clips 18, thereby electrically earthing the wire. As is evident from the other Figures described below, the clips 18 include a strap 20 and a pair of mating connectors 22, 24. Two openings 28, 30 extend through the strap 20 and the stripped wire 12 is threaded through one of these openings and out through the other. The clip is placed around the pipe, formed into a closed loop and secured tightly around the pipe by engaging the mating connecting members 22, 24. In this way, the earth bond cable 10 is clamped securely against each pipe 16 by a length of wire equal to the internal circumference of the strap 20 between the openings. Thus, a predetermined length of cable sufficient to establish a good earth bond is in electrical contact with the pipes 16. The end of the cable 12 may be severed, as at 26, once the clips 18 have been secured. The part of the earth bond cable lying against the pipe 16 is securely clamped against the surface of the pipes 16, ensuring a high-integrity connection.

So long as the wire 12 extends between the openings in the strap 20, it is not possible for the electrician fitting the earth bond to use an insufficient length of earth bond cable for providing the connection to the pipe/rod since the amount of cable in contact with the pipe/rod is determined by the separation between the openings in the strap 20 and thus all connections achieved by the clips 18 are consistent with each other and of high integrity.

Referring now to Figures 2 to 4, the clip is shown in greater detail. The clip has a strap 20 with a tongue 22 provided at one end; the tongue has a series of teeth formed on its upper and lower surfaces. At the other end of the strap, a toothed pair of jaws 24 is provided and the internal surface of each jaw has a row of teeth that can engage with the teeth on the top and bottom surfaces of the tongue 22. Thus, by pushing the tongue 22 between the pair of jaws 24 (see arrow A in Figure 2), the clip can be fastened on to each of the pipes 16. The tongue 22 will be pushed into the jaws 24 for a sufficient distance to clamp the stripped earth bond wire 12 tightly against the water pipe 16 with the required pressure. As already described, the strap 20 includes a pair of openings 28, 30 through which the stripped wire 12 can be threaded. A channel 31 is provided along the internal surface of the strap between openings 28 and 30. The channel is bordered by a row of lugs 32 that help locate the wire 12 within the channel 31. The gap between adjacent lugs in a row allows inspection of the wire 12 when clamped to the pipe 16. The lugs of one row are offset with respect to the lugs of the other row so that the full length of the wire can be inspected if necessary.

A tapered tongue 34 is provided below the toothed tongue 22; the tapered tongue slides under the lower jaw 24 when the tongue 22 is pushed between the jaws 24.

This provides a consistent pressure over the circumference of the pipe 16 and avoids discontinuities that could impose an excessively high local pressure that might dent the pipe.

The form of the tongue and jaw mating connectors 22, 24 is more fully described in UK patent 1,600,601. The clip may be made, e.g. out of UN-stabilised high temperature nylon 66, by injection moulding.

As described in UK patent 1,600,601, the clip can be unfastened by pushing the tongue 22 axially with respect of the jaws 24 (as shown by arrow B in Figure 2) and this may be desirable in the early stages of fastening the clip if the alignment of the clip or cable is incorrect. However, for electrical safety reasons, it is not desirable that the clip can be removed from the earth pipe/rod since earth bonding is a permanent requirement of electrical regulations. Accordingly, to prevent disengagement once the clip has been fully secured, tabs 38 are integrally moulded on either side of the jaws 24 that prevent the tongue from being moved out through the side of the jaws, i.e. axially in the direction of arrow B (see Figure 3) when more than three teeth on the tongue/jaws 22, 24 have been engaged. The inside perimeter of the clip may include a frictional section, that has a high coefficient of friction with the pipe so that once the clip is engaged on the pipe 16 the frictional section will not allow the clip to be easily displaced from its position. The frictional section may be teeth that "bite" into the pipe/rod or a roughened area, e.g. carborundum.

Claims

1) A clip for establishing a connection between an earth bond cable and extraneous metalwork or other conductive object, the clip comprising a flexible strap having two ends, a first mating connector secured at the first end of the strap and a second mating connector secured at the second end of the strap, the two mating connectors being capable of mating with each other to orm the clip into a closed loop and securing the strap around the conductive object, wherein the clip comprises at least one opemng extending through the clip (and preferably through the strap) through which an earth bond cable may be fed, the arrangement being such that an electrically conductive earth bond cable can be fed through the opening and the clip can be secured to the conductive object by inter-engaging the mating connectors so as to clamp the earth bond cable between the clip and the conductive object.

2) A clip as claimed in claim 1, wherein the mating connectors of the clip are rows of teeth that can interengage with each other to secure the clip around the conductive object and preferably a double row of teeth.

3) A clip as claimed in claim 1 or claim 2, which includes two spaced apart openings such that the earth bond cable can be threaded through one opening and out of the other opening, thereby ensuring that there is at least an assured length of earth bond cable in contact with the extraneous conductive metalwork corresponding to the distance between the openings along the inside perimeter of the clip.

4) A clip as claimed in any one of claims 1 to 3, wherein the inside surface of the strap includes a channel for holding the earth bond cable in place while the clip is secured to the conductive object. 5) A clip as claimed in claim 4, when dependent on claim 3, wherein the channel extends between the two openings.

6) A clip as claimed in claim 4 or claim 5, wherein the channel is formed between lugs, the lugs preferably being spaced apart by a gap that allows inspection of the earth bond cable once it has been clamped to the conductive object.

7) A clip as claimed in any one of claims 1 to 6, wherein the inside surface of the strap includes a section having a greater coefficient of friction than the rest of the surface so that once the clip is engaged on the pipe, the frictional engagement of the section with the conductive object will resist displacement of the clip.

8) A method of securing an earth bond cable to metalwork or other conductive object, e.g. a pipe or rod, using a clip as claimed in claim 1, comprising threading the cable through the opening in the clip and securing the strap against the conductive object so as to clamp the earth bond cable between the clip and the object.

9) A method as claimed in claim 8, wherein the mating connectors of the clip are rows of teeth and the method comprises interengaging the rows of teeth to secure the clip around the conductive object.

10) A method as claimed in claim 8 or claim 9, wherein the clip includes two spaced apart openings and the method comprises threading the earth bond cable through one opening and out through the other opening, thereby ensuring that there is at least an assured length of earth cable in contact with the conductive object corresponding to the distance between the openings along the inside perimeter of the clip.

11) A method as claimed in any one of claims 8 to 10, wherein the conductive object is a rod, pipe or other electrically conductive rounded object within a building having an electrical installation, thereby providing equal potential bonding throughout the building's electrical installation.